DESCRIPTION: This proposal aims to understand the fundamental aspects of the relationship between the heme prosthetic group of hemeoproteins and the surrounding polypeptide chain and protein matrix, through a combination of high resolution optical and infrared spectroscopy, together with detailed electrostatic potential calculations. Dr. Vanderkooi makes a compelling case that for no other class of prosthetic group proteins is there such a rich experimental data base, tractable prosthetic group and well-defined link between the properties of the active center, the protein motional dynamics and the overall function of the protein, as there is for heme proteins. Dr. Vanderkooi chooses cytochrome c and cytochrome c peroxidase (CCP) as examples of c-type hemoproteins that form specific protein-protein complexes involved in electron transfer, and the hemoglobin/myoglobin systems as histidine ligated -protoporphyrin IX containing oxygen transport proteins. High resolution hole burning optical spectroscopy, FTIR, and fluorescence emission experimental protocols are coupled with theoretical calculations of electrostatic field effects on optical transitions, as perturbed by protein motion, vibrational coupling and low temperature stabilized conformational substates.